1. Field of the Invention
The present invention relates to a light guide for generating a plurality of linear beams from light emitted by a light source, and the invention also relates to an illuminating device using the light guide and an image reading apparatus using the same.
2. Description of Related Art
Examples of the aforementioned light guide include those described in Japanese Laid-Open Patent Publication No. 2014-187444 and U.S. Pat. No. 8,279,499. Such a conventional light guide is opposed at one end surface to a light source. Incident light from the light source is split by a splitting section and introduced into a plurality of rod-like light guiding sections arranged side by side widthwise. The introduced light propagates through each of the rod-like light guiding sections lengthwise while repeatedly experiencing total reflection within the light guiding section.
Furthermore, each rod-like light guiding section is provided on the bottom with a reflective section (e.g., a group of prisms) capable of reflecting the introduced light upward. Moreover, the rod-like light guiding section has an emission surface provided on the top so as to be opposed to the reflective section. The emission surface is designed so as to turn the introduced light from, for example, the opposing reflective section into a linear beam and direct the beam to a predetermined position.
However, in the conventional light guide, the splitting section and the rod-like light guiding sections are simply connected at an angle, so that the splitting section and the light guiding sections allow the light to propagate in different directions. Accordingly, the light introduced from light-receiving ends of the rod-like light guiding sections is, for example, uneven in light intensity in the width direction of the light guide, as shown in, for example, FIG. 12 of Japanese Laid-Open Patent Publication No. 2014-187444. Therefore, to preclude such uneven light intensity of the conventional light guide, it is necessary to lengthen the rod-like light guiding sections, thereby achieving a sufficient entrance length.
Furthermore, in the case where a sufficient entrance length is not ensured, even if the reflective section is disposed at the light-receiving end of each rod-like light guiding section, light might not be incident on the reflective section in a desired manner. As a result, cross-sectional light distribution at the light-receiving end becomes irregular compared to the rest of the rod-like light guiding section.